1. Field of the Invention
The present invention relates to a magnetic tape cartridge having a single reel of magnetic tape rotatably retained therein.
2. Description of the Related Art
Conventionally, the magnetic tape cartridge having a single reel of magnetic tape rotatably retained therein has been known as a type of magnetic tape cartridge used as the recording medium of an external storage device of computers, etc. as described, for example, in Japanese Unexamined Patent Publication Nos. 11(1999) -306722, 2001-148179, and 2001-266533.
FIG. 4 is a perspective view of a magnetic tape cartridge 1 of this type, illustrating an overall structure of the cartridge with a sliding door 11 opened. On a side wall of a cartridge case 4 composed of an upper case 2 and a lower case 3 firmly fixed together as a unit, a tape reeling-out opening 10 that extends to the upper and lower cases 2 and 3 is formed in the vicinity of a corner section. The tape reeling-out opening 10 has a sliding door 11 which is slidable to open and close the opening 10. A magnetic tape 6 is used as a data storage medium of computers and the like, and has a leader pin 5 firmly fixed at the end, which is engaged by a pin holding member of a magnetic tape cartridge read/write apparatus for reeling out the magnetic tape 6 from the cartridge case 4, and loading onto the magnetic tape cartridge read/write apparatus when the magnetic tape cartridge 1 is loaded therein. The magnetic tape cartridge read/write apparatus is configured and adapted to rewind the magnetic tape onto the reel 7 and bring back the leader pin into the cartridge when the magnetic tape cartridge is unloaded.
The cartridge case 4 is composed of the upper case 2 and lower case 3 made of a synthetic resin firmly fixed together as a unit, e.g. by screws as described, for example, in Japanese Unexamined Patent Publication No. 2001-148179, or by ultrasonic welding on the mating surfaces of the side walls of the upper and lower cases 2 and 3 as described, for example, in Japanese Unexamined Patent Publication No. 2001-266533. The leader pin 5 is removably retained across the upper and lower cases with the axis line in up-down direction in the vicinity of the tape reeling-out opening 10 provided on the cartridge case 4, and the sliding door 11 for opening and closing the tape reeling-out opening 10 is urged by a spring toward a position to close the opening 10.
In the magnetic tape cartridge 1 structured as described above, the tape reeling-out opening 10 is formed in the vicinity of a corner of the generally square cartridge case 4, and a space for the pathway of the magnetic tape and the access path to the leader pin 5 by the pin holding member of the magnetic tape read/write apparatus needs to be secured around the place where the leader pin 5 is retained inside the opening 10, so that the screws for fixing the upper and lower cases can not be used in that area, and consequently they are provided in places away from that area as described, for example, in Japanese Unexamined Patent Publication No. 2001-148179. Therefore, the area of the cartridge case 4 in the vicinity of the tape reeling-out opening 10 has a low strength, since the area has no fixed portion secured by screws, as well as no side wall because of the opening 10, and moreover, a lead-in recess 20 for the leader pin 5 is formed on the bottom surface of the lower case 3.
In handling the magnetic tape cartridge 1, the cartridge may be sometimes dropped accidentally on the floor, and if it falls with the corner having the tape reeling-out opening 10 facing downwards, crashing the weak corner in bond strength against the floor, the case 4 is likely to be damaged with the broken or cracked corner.
In this connection, it may be contemplated that the upper and lower cases are welded together as described, for example, in Japanese Unexamined Patent Publication No. 2001-266533, in order to increase the bond strength. But a portion of a weld deposit jointing the mating surfaces of the upper and lower cases may stick out of the mating surfaces, thereby cosmetic appearance is spoiled. In addition, the portion of the weld deposit sticking out of the mating surfaces may come off by frictions and contaminates the working environment. Further, a portion of the weld deposit may get into the case by the vibration of the ultrasonic horn during the welding process, and turns into so-called welding dust which causes degradation in the quality of the magnetic tape cartridge.